This easy STEM experiment has major wow factor, even for grown-ups!

In an empty water bottle, poke three small holes with a needle, one atop the other. Many water bottles these days are made of incredibly thick plastic: you’ll want to look for good old-fashioned thin plastic bottles if you’re going to pierce through with the needle easily.

We added a little blue food coloring to the empty bottle just for fun, although the experiment will work just fine with clear water.

Begin pouring water in (a watering can is helpful to use), and of course water will begin trickling out of your three holes slowly. Once your bottle is full, twist on the cap.

The water stops leaking out!

After your child’s initial moment of wow, you can explain what’s going on: the bottle contains both air and water, but for more water to be pushed out, more air has to come in. Once the cap is on, the water molecules bunch together and create enough surface tensions against the tiny holes from the needle. If the holes were any larger, of course, this wouldn’t work so well! Then, once the cap is off, more air comes in and pushes the water right out again.

With that explanation out of the way, now Travis wanted to twist the cap on and twist the cap off over and over… Through three refills of the bottle!

There might have been a giggle factor to this project, too, since yes the bottle looks a bit like it’s going to the bathroom when the stream of water arcs out.

As you can see, both my kids were rapt! A fantastic STEM experiment outside on a hot day.